Dynamic cycle air conditioner with incremental dehumidification in an indirect evaporative cooler

ABSTRACT

Dynamically cycling of air in an indirect evaporative cooler. A heat exchanger includes a dry passage separated from a wet passage by a membrane, the dry passage including an intake portion, an outlet portion, and a loop portion. By selectively passing intake air from the intake portion and/or recirculation air from the loop portion using a mixing valve, air is moved into and through the loop portion. The air within the heat exchanger can be selectively passed outside through the outlet portion and/or recirculated by the mixing valve. In this manner air is able to be circulated a number of loop circuits through the loop portion, enabling cooling and/or dehumidifying of air.

FIELD OF THE INVENTION

Embodiments according to the present disclosure generally relate to air conditioning and, more specifically, to an indirect evaporative air conditioning system incorporating dehumidification.

BACKGROUND OF THE INVENTION

Direct evaporative coolers, employing the thermodynamic principle of adiabatic saturation, are well-known in the art. Air to be cooled is saturated with an evaporative liquid (e.g., a water mist), whose evaporation from the liquid state (mist) to vapor state takes up available (latent) heat energy from the air itself, thereby lowering its temperature. The ambient air may be cooled in the limit to its wet bulb temperature using direct evaporative cooling, the wet bulb temperature also being known as the adiabatic saturation temperature. A problem with direct evaporative cooling is the introduction of humidity into the cooled environmental space, making this method of cooling unsuitable for sustained cooling of a confined habitable space because continuous humidification of the air causes discomfort to occupants.

A different method of cooling air is termed indirect evaporative cooling, which functions by evaporating a cooling liquid, usually water, into a first air stream while transferring heat from a second air stream to the first air stream. Conventional indirect evaporative coolers have traditionally been more expensive than their evaporative counterparts. In particular, inefficiencies in the transfer of heat from the second air stream to the first air stream in conventional systems prevent sufficient cooling of air at a similar cost to evaporative coolers. These inefficiencies can be the result of a poor water supply system and/or expensive heat exchanger materials, air flow pressure issues, a large number of components that are auxiliary to the indirection evaporative cooling system, etc.

SUMMARY OF THE INVENTION

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

An embodiment of the present disclosure includes dynamically cycling air in an indirect evaporative cooler. A heat exchanger includes a dry passage separated from a wet passage by a membrane, the dry passage including an intake portion, an outlet portion, and a loop portion. By selectively passing intake air from the intake portion and/or recirculation air from the loop portion using a mixing valve, air is moved into and through the loop portion. The air within the heat exchanger can be selectively passed outside through the outlet portion and/or recirculated by the mixing valve. In this manner air is able to be circulated a number of loop circuits through the loop portion, enabling cooling and/or dehumidifying of air.

More specifically, an aspect of the present disclosure provides indirect evaporative cooler apparatus including: a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; a first fan disposed downstream of the mixing valve and adapted to move a first volume of air into and through the loop portion; a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the mixing valve, the first fan, the diverting valve, and a combination thereof, to circulate air a number of loop circuits through the loop portion for cooling and dehumidifying the first volume of air.

In an embodiment of the indirect evaporative cooling apparatus the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof. In a further embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value. In a further embodiment the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value. In a further embodiment the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value. In an embodiment the indirection evaporative cooling apparatus includes a water source having an associated pressure valve, and a nozzle configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane. In a further embodiment the controller is adapted to set a water pressure of the water source. In an embodiment the indirect evaporative cooling apparatus further includes a water nozzle disposed within the dry passage and adapted to dispense condensed water from the first volume of air. In a further embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water.

According to another aspect of the present disclosure, a method of dynamically cycling air in an indirect evaporative cooler includes: having a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; selectively passing intake air from the intake portion, recirculation air from the loop portion, or a combination thereof by a mixing valve disposed in the dry passage; moving air into and through the loop portion by a first fan disposed downstream of the mixing valve; selectively passing outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof by a diverting valve disposed in the dry passage; and circulating air a number of loop circuits through the loop portion for cooling and dehumidifying the first volume of air by a controller adapted to operate the mixing valve, the first fan, the diverting valve, and a combination thereof.

In an embodiment of the method the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof. In a further embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value. In a further embodiment the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value. In a further embodiment the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value. In an embodiment the method further includes wetting the wet passage by a water source having an associated pressure valve and a nozzle, for evaporative cooling of the substantially liquid-impermeable membrane. In a further embodiment the controller is adapted to set a water pressure of the water source. In an embodiment the method further includes dispensing condensed water from the first volume of air by a water nozzle disposed within the dry passage. In a further embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water.

According to another aspect of the present disclosure, a system for dynamically cycling air includes: an evaporative liquid reservoir comprising a pressure valve and a channel adapted to transport evaporative liquid; a heat exchanger comprising: a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a nozzle coupled with the channel and configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; and a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the pressure valve, the mixing valve, the diverting valve, and a combination thereof, to circulate air a number of loop circuits through the loop portion for cooling and dehumidifying a first volume of air.

In an embodiment the system further includes a first fan disposed downstream of the mixing valve and adapted to move the first volume of air into and through the loop portion. In an embodiment the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof. In an embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value. In an embodiment the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value. In an embodiment the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value. In an embodiment the controller is adapted to set a water pressure of the evaporative liquid reservoir. In an embodiment the system further includes a water nozzle disposed within the dry passage and adapted to dispense condensed water from the first volume of air. In an embodiment the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.

FIG. 1 is an illustration depicting an exemplary indirect cooling apparatus, according to an embodiment of the present disclosure.

FIG. 2 is a cross-section of a portion of an exemplary indirect cooling apparatus including a dry passage and a wet passage, according to an embodiment of the present disclosure.

FIG. 3 depicts an exemplary cooling and dehumidifying sequence via a psychrometric chart, according to an embodiment of the present disclosure.

FIG. 4 is a block diagram depicting an exemplary air conditioning application according to an embodiment of the present disclosure.

FIG. 5 illustrates an exemplary process of conditioning air in an indirect evaporative air conditioner, according to an embodiment of the present disclosure.

FIG. 6 illustrates a block diagram of an exemplary air conditioning device configured to implement an air conditioning application according to some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

Some portions of the detailed description that follows are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer generated step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present claimed subject matter, discussions utilizing terms such as “storing,” “creating,” “protecting,” “receiving,” “encrypting,” “decrypting,” “destroying,” or the like, refer to the action and processes of a computer system or integrated circuit, or similar electronic computing device, including an embedded system, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

Dynamic Cycling and Incremental Dehumidification of Air in Indirect Evaporator

In one embodiment of the present disclosure, an indirect evaporative cooler apparatus is able to cycle air dynamically through one or more dry passages of the indirect evaporative cooler, for cooling and/or dehumidification of a volume of air. Indirect evaporative cooling describes cooling in which an airstream is first cooled by adiabatic saturation, and then used to cool a separate, non-mixing airstream across a heat-transfer partition (e.g., an airstream of a wet passage is in thermodynamic communication with an airstream of a dry passage). The latter airstream is said to be sensibly cooled; that is, cooled without altering its absolute moisture content.

Referring now to FIG. 1, an exemplary indirect evaporative cooling apparatus is depicted according to an embodiment of the present disclosure. Indirect evaporative cooling apparatus 100 includes a controller 103 operable to control valves, fans, pumps, and other components of indirect evaporative cooling apparatus 100 according to embodiments of the apparatus as described herein. Indirect evaporative cooling apparatus 100 includes an intake portion 105, a mixing valve 110, a loop portion 115, an outlet portion 120, and a diverting valve 125. Indirect cooling apparatus 100 includes one or more dry passages, and one or more wet passages. Dry passages and wet passages are thermodynamically coupled, such that a volume of air transported through a dry passage can be cooled, indirectly, via evaporative cooling occurring in a wet passage. The volume of air can be transported into and through the dry passage by a fan 135, which according to an embodiment is disposed such that the mixing valve 110 is between the fan 135 and the intake portion 105 and a return portion of loop portion 115.

According to an embodiment, one or more nozzles 130 (e.g., a layer nozzle) are disposed above the one or more wet passages, the nozzles 130 configured to dispense water (or other suitable liquid) for wetting a surface of wet passage for evaporative cooling. According to an embodiment one or more dry passage nozzles 140 are disposed within the one or more dry passages, and are configured to expel water from within the dry passage. The water may accumulate, for example, via condensation from a dehumidifying function of the indirect evaporative cooling apparatus 100. The nozzle 140 can be disposed to expel the condensed water onto a surface of a wet passage located below the nozzle 140. Alternatively, the nozzle 140 can be disposed to expel the condensed water to be collected in a water reservoir, for example an external reservoir 145 and/or an internal water reservoir 165. While not shown, indirect evaporative cooling apparatus 100 can include one or more barometers, hygrometers (humidity sensors), and thermometers, that are operable to measure their respective environmental conditions in the dry and/or wet passages, and to report corresponding values to controller 103.

According to an embodiment, an external reservoir 145 supplies an evaporative liquid to nozzles 130 for wetting of wet passages of the indirect evaporative cooling apparatus 100. The evaporative liquid can be water, for example, although other liquids suitable for evaporative cooling in wet passages of the indirect evaporative apparatus 100 can be used, as is appreciated by those of skill in the art. The external reservoir 145 can have an associated pressure valve 150, along with a supply pipe 155 and a supply pump 160. According to embodiments of the present disclosure, a supply pressure of nozzles 130 is set by pressure valve 150, controlled by controller 103. According to an embodiment, indirect evaporative cooling apparatus 100 includes a manifold 180 arranged to house one or more nozzles 130 and to dispense evaporative liquid over the one or more wet passages. According to an embodiment, an optional internal water reservoir 165 is located to accumulate from nozzles 130 and/or condensed water from nozzles 140. The internal water reservoir can include an associated supply pipe 170 and pump 175 to provide accumulated water for dispensing from nozzles 130 (e.g., via optional manifold 180).

As depicted in FIG. 1, the dry passage can be arranged in a serpentine arrangement such that a volume of air is transported from the intake portion 105 and follows a number of turns before arriving at the diverting valve 125. The wet passage can follow a substantially similar course as the dry passage, such that thermodynamic communication is maintained between the dry and wet passage. According to an embodiment the serpentine arrangement is descending, that is, with the intake portion 105 being positioned higher (e.g., at a greater gravitational or pressure potential) than the outlet portion 120. The diverting valve 125 is disposed upstream of the loop portion 115 and the outlet portion 120 with regard to the direction of air travel, and is operable to pass the volume of air through the outlet portion 120, the loop portion 115, a combination thereof, or to close both pathways 120 and 115. The diverting valve 125 is under controller 103 control. Optionally, a fan 185 can be included disposed upstream of diverting valve 125, fan 185 under control of controller 103 and operable to assist the movement of the volume of air through the dry passage. For example, optional fan 185 can assist in moving the volume of air in recirculation toward mixing valve 110, and/or toward outlet portion 120.

According to some embodiments of the present disclosure, some portions of the dry passage include one or more elements to induce a pressure differential within the dry passage (e.g., air traps 190 or a heat exchange coil, not shown). Additionally or alternatively, indirect evaporative cooling apparatus 100 can include an exhaust pipe (not shown) having an associated exhaust valve (not shown) and exhaust fan (not shown), disposed on an enclosure of apparatus 100 and operable to develop a negative pressure differential in the one or more wet passages relative to ambient pressure. These features, as well as other characteristics of the indirect evaporative cooling apparatus of the present disclosure, can be better appreciated by a description of the internal components and functions of the indirect evaporative cooling apparatus herein.

Referring now to FIG. 2, a cross section A-A of FIG. 1 is depicted according to an exemplary embodiment of the indirect evaporative cooling apparatus 100. FIG. 2 depicts a number N of parallel dry passages 203. As shown, dry passages 203 have a hexagonal cross-section 205, although it is appreciated by those of skill in the art that other cross-section configurations (circular, oval, square, etc.) are possible. In between portions of dry passages 203 are wet passages 210. An expanded view of a portion of dry passage 203 depicts nozzle 230 configured to wet the wet passages 210, and a nozzle 240 configured to expel any accumulated water from dry passages 203. Separating dry passages 203 and wet passages 210 is a substantially liquid impermeable membrane 215, providing thermodynamic communication between dry passages 203 and wet passages 210 while preventing fluid to flow freely there between. According to an embodiment of the present disclosure membrane 215 includes a hydrophilic surface oriented toward wet passages 210, and a hydrophobic surface oriented toward dry passages 203. In this manner wet passages 210, when wet (e.g., from nozzle 130) will preferentially retain liquid to be used for evaporative cooling. Meanwhile, surfaces of dry passages 203 repel any water introduced, for example via condensation from dehumidification of a volume of air passing through dry passages 203, easing the removal of condensed water from dry passages 203 (e.g., via nozzles 140). According to an embodiment of the present disclosure the indirect evaporative cooling apparatus 100 includes an internal water reservoir 265, which is configured to receive water from nozzles 230 and/or nozzles 240. The collected water can be recycled, that is, used again to dispense water over wet passages 210 via nozzles 230 for evaporative cooling of membrane 215 (and induced cooling of a volume of air traveling through dry passages 203).

Referring now to FIG. 3, an exemplary cooling and dehumidifying sequence for a volume of air moving through a dry passage of the indirect evaporative cooling apparatus is depicted via psychrometric graph, according to an embodiment of the present disclosure. As seen in FIG. 3 at location A there is relatively hot and humid air, corresponding to an initial state of a volume of air that is directed to move through the dry passage (e.g., intake air through intake portion 105 of apparatus 100). As the volume of air moves through the dry passage and is cooled via indirect evaporative cooling (e.g., evaporative cooling in thermodynamically coupled wet passage), the volume of air is reduced in temperature without gaining moisture. That is, the specific humidity of the volume of air remains constant, while the relative humidity increases to substantially the dew point (due to the decrease in temperature of the volume of air). This is represented by the transition between locations A and B on the psychrometric graph of FIG. 3. The transition from locations A and B on the psychrometric graph can correspond to a number of circuits of the volume of air through the loop portion of a dry passage, where each circuit leads to further cooling of the volume of air.

Once the volume of air substantially reaches its dew point (based on the specific humidity of the air upon intake at intake portion 105), further cooling of the now-saturated air (100% relative humidity) causes condensation of water from the volume of air. This is represented by the transition from locations B and C on the psychrometric graph. At location C the volume of air has been both cooled from its initial temperature at location A, and dehumidified from its initial specific humidity (locations A and B). The transition from locations B and C on the psychrometric graph can correspond to a further number of circuits of the volume of air through the loop portion of a dry passage, where each circuit leads to further cooling and dehumidification of the volume of air. This may be termed incremental cooling and/or dehumidification. By incremental it is meant incorporating the dehumidification processes and the cooling process, e.g., each cooling cycle the volume of air is dehumidified as well as cooled. In this manner the volume of air, as it circulates in the dry passage of the indirect evaporative cooling apparatus, is cooled and dehumidified bit by bit, each cycle (e.g., circuit of air through a dry passage) resetting the starting conditions of the volume of air. According to an embodiment of the present disclosure, condensed water is removed from the dry passage during this incremental cooling and dehumidification process, as described herein.

Referring now to FIG. 4 a block diagram depicts an exemplary air conditioning application according to an embodiment of the present disclosure. Air conditioning application 400 can be embodied on a memory and executed by a processor of a computing device, for example controller 103. Air conditioning application 400 includes an inputs module 405, a controls module 410, and an output module 420. Inputs module 405 is configured to receive data regarding environmental conditions of the indirect evaporative cooling apparatus, such as a temperature of a dry passage and/or a wet passage, a humidity of a dry passage, and a pressure of a dry passage and/or a wet passage. Data can be generated from appropriate sensors (e.g., thermometers, hygrometers, barometers), which according to an embodiment can be located at various locations throughout the indirect evaporative cooling apparatus.

Controls module 410 is configured to send control signals to components of indirect evaporative cooling apparatus determined, from environmental conditions of the indirect evaporative cooling apparatus. Components of the indirect evaporative cooling apparatus that are controlled by controls module 410 include mixing valve 110 and intake fan 135, diverting valve 125, optional fan 185, and optional exhaust valve and fan. Controls module 410 can also control operation of reservoir valve 150, pump 160, and optional internal reservoir pump 175, along with any other electromechanical components included in the indirect evaporative cooling apparatus of the present disclosure.

Output module 420 delivers control signals to the components of the indirect evaporative cooling apparatus according to the operations determined by controls module 410. Exemplary operations include: single cycle operation; dynamic cycle operation; high pressure operation; low pressure operation; and water operation.

In single cycle operation a volume of air is controlled to move once through the dry passage(s) of the indirect evaporative cooling apparatus, which may be accomplished by opening mixing valve 110 to air from intake portion 105, and diverting valve 125 to outlet portion 120 only—that is, not mixing the volume of air through loop portion 115. Fan 135 (and/or optional fan 185) can be operated to enhance the movement of the volume of air through the dry passage(s).

In dynamic cycle operation initially mixing valve 110 is opened to air from intake portion 105, and then mixing valve 110 is closed to intake portion 105 in order to introduce a first volume of air to dry passage(s). Movement of the first volume of air through the dry passage(s) can be enhanced by operation of fan 135 and/or optional fan 185. Diverting valve 125 is controlled to close air movement to outlet portion 120, and to re-circulate the first volume of air through loop portion 115. In this manner the first volume of air can be made to circulate through the dry passage(s) a number of times, and to be continuously cooled via indirect evaporative cooling. According to embodiments of the present disclosure, dynamic cycling of a volume of air through the indirect evaporative cooling apparatus is used to dehumidify the volume of air, as well as to cool, as is described further herein below.

In high pressure operation mixing valve 110 is opened to air from intake portion 105 and diverting valve 125 is closed to outlet portion 120—that is, the volume is air is not expelled from the indirect evaporative cooling apparatus. Fan 135 (and/or optional fan 185) can be operated to enhance the movement of the volume of air into the dry passage(s). In an embodiment, diverting valve 125 is closed so that the volume of air is not diverted to loop portion 115. In an embodiment, diverting valve 125 is open to loop portion 115 (but closed to outlet portion 120), such that air is re-circulated through the dry passage(s) (e.g., for pressurization and cooling of the volume of air in the dry passage).

In low pressure operation the wet passage(s) of the indirect evaporative cooling apparatus develop of a lower pressure, with respect to the ambient pressure and/or the pressure in dry passage(s). A lower pressure in the wet passage(s) encourages evaporation of liquid at surfaces of the wet passage(s), enhancing the indirect cooling effect. According to an embodiment of the present disclosure, the indirect evaporative cooling apparatus includes an exhaust fan and valve in an enclosure. The exhaust fan and valve can be operated by controller 103 to force air out of wet passage(s) of the indirect evaporative cooling apparatus, and to thereby develop a low pressure in the wet passage(s) (e.g., a negative pressure with respect to ambient and/or dry passage pressure).

In water operation the components of the external reservoir 145 and of optional internal water reservoir 165 are controlled to store and distribute liquid for evaporative cooling of wet passages of the indirect evaporative cooling apparatus. Output module 420 can signal reservoir valve 150 to open or close, and pump 160 to operate to move liquid to external reservoir 145. In some embodiments pump 160 is operated to pressurize external reservoir 145, in order to increase a water pressure and/or a rate at which wet passage water nozzles dispense water. In an embodiment output module 420 signals optional internal reservoir pump 175 to close in order to retain accumulated water. In an embodiment output module 420 signals optional internal reservoir pump 175 to pump water up to be dispensed over wet passages, for example via optional manifold 180. In an embodiment valve 150 is signaled to open in order to return accumulated water in internal reservoir 165 to external reservoir 145. Valve 150 operation can be determined from one or more of: dry passage and/or wet passage temperature; temperature of water in internal reservoir 165 and/or external reservoir 145; a water level of internal reservoir 165 and/or external reservoir 145.

Indirect Evaporation via Pressure Differentials

According to some embodiments of the present disclosure, for air stream detected to be substantially on its dew point, dehumidification of the air stream can be accomplished via pressure differentials within regions of the indirect evaporative cooling apparatus 100. According to some embodiments of the present disclosure, some portions of the dry passage include one or more elements to induce a pressure differential within the dry passage, for example air traps 190 and/or a heat exchange coil (not shown). Air traps 190 are disposed on one or more surfaces of the dry passage(s), and function to cause regions of increased pressure within an airstream moving through the dry passage. A higher pressure within a saturated, or nearly saturated, airstream is able to cause condensation of water from the airstream (e.g., dehumidification). Additionally or alternatively, an indirect evaporative cooling apparatus of the present disclosure can include an exhaust pipe (not shown) having an associated exhaust valve (not shown) and exhaust fan (not shown), disposed on an enclosure of apparatus and operable to develop a negative pressure differential in the one or more wet passages relative to ambient pressure. A reduced pressure in a wet passage of the indirect evaporative cooling apparatus is able to increase an evaporation of a liquid wetting a surface of the wet passage, and thereby to increase cooling of the airstream in the adjacent dry passage.

FIG. 5 illustrates an exemplary process 500 of conditioning air in an indirect evaporative air conditioner, according to an embodiment of the present disclosure. Step 501 includes circulating a first volume of air through a loop portion of a dry passage of an indirect evaporative air conditioner (e.g., apparatus 100). According to an embodiment, the dry passage is in thermodynamic communication with a wet passage that is configured to receive and to evaporate a liquid. The dry passage and the wet passage together form a heat exchanger (e.g., dry passage 203, wet passage 210, membrane 215 of FIG. 2).

Step 503 includes determining a relative humidity of the first volume of air. The relative humidity can be determined based on a barometric pressure and/or a temperature in the dry passage. According to an embodiment, the indirect evaporative cooling apparatus can determine the barometric pressure and/or the temperature from an included one or more barometers, hygrometers (humidity sensors), and thermometers, that are operable to measure their respective environmental conditions in the dry and/or wet passages, and to report corresponding values to a controller (e.g., controller 103 of FIG. 1).

Step 505 includes selectively generating a pressure differential in the heat exchanger upon the first volume of air determined to be substantially at its dew point, by increasing barometric pressure in the dry passage, decreasing barometric pressure in the wet passage, or a combination thereof, sufficient to condense water from the first volume of air. The selective pressure differential generation can be accomplished using a controller 103 running an air conditioning application 400, for example by performing a high pressure operation, a low pressure operation, or a combination of these as described herein.

Water Conservation in Indirect Evaporator

According to an embodiment of the present disclosure water condensed from a dehumidification process of a volume of air moving through an indirect evaporative cooler can be captured and/or recycled for use in subsequent wetting of one or more wet passages of the indirect evaporative cooler. In this manner water is conserved from the incoming air stream, which, as it cools in a dry passage, approaches its dew point and then commences condensation of water contained in the air stream. This condensed water can gather on a surface of a dry passage (e.g., hydrophobic surface of a dry passage 203), and can be expelled from the dry passage. One means of expelling condensed water is by a water nozzle (e.g., water nozzle 240). The removal of condensed water from a dry passage can be aided by increasing the pressure within the dry passage, with respect to ambient pressure (and/or with respect to the wet passage).

According to an embodiment of the present disclosure an indirect evaporative cooling apparatus (e.g., apparatus 100) includes an internal water reservoir (e.g., reservoir 265), which is configured to receive water from wet passage nozzles and/or dry passage nozzles. Alternatively or additionally, captured water can be returned to an external liquid reservoir (e.g., reservoir 145).

The collected water can be recycled, that is, used again to dispense water over wet passages 210 via nozzles 230 for evaporative cooling of membrane 215 (and induced cooling of a volume of air traveling through dry passages 203).

Exemplary Computing Device

FIG. 6 illustrates a block diagram of an exemplary air conditioning device 600 configured to implement an air conditioning application 400 according to some embodiments. The air conditioning device 600 is able to be one or more of the indirect evaporative cooling apparatuses 100, including controller 103 and/or other computing devices that are able to acquire, store, compute, communicate and/or display information such as images and videos. In general, a hardware structure suitable for implementing the air conditioning device 600 includes a network interface 602, a memory 604, a processor 606, I/O device(s) 608, a bus 610 and a storage device 612. Alternatively, one or more of the illustrated components are able to be removed or substituted for other components well known in the art. The choice of processor is not critical as long as a suitable processor with sufficient speed is chosen. The memory 604 is able to be any conventional computer memory known in the art. The storage device 612 is able to include a hard drive, CDROM, CDRW, DVD, DVDRW, flash memory card or any other storage device. The air conditioning device 600 is able to include one or more network interfaces 602. An example of a network interface includes a network card connected to an Ethernet or other type of LAN. The I/O device(s) 608 are able to include one or more of the following: keyboard, mouse, monitor, display, printer, modem, touchscreen, button interface and other devices. As described above, the air conditioning application 630 is to be stored in the storage device 612 and memory 604 and processed as applications are typically processed. Greater or fewer components than shown in FIG. 6 are able to be included in the air conditioning device 600. In some embodiments, air conditioning hardware 620 is included. Although the air conditioning device 600 in FIG. 6 includes the air conditioning application 630 and air conditioning hardware 620, the air conditioning functions described herein are able to be implemented on the air conditioning device 600 via hardware, firmware, software separately, or any combination thereof.

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as may be suited to the particular use contemplated.

Embodiments according to the invention are thus described. While the present disclosure has been described in particular embodiments, it should be appreciated that the invention should not be construed as limited by such embodiments, but rather construed according to the below claims. 

What is claimed is:
 1. An indirect evaporative cooler apparatus comprising: a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; a first fan disposed downstream of the mixing valve and adapted to move a first volume of air into and through the loop portion; a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the mixing valve, the first fan, the diverting valve, and a combination thereof, to circulate air a number of loop circuits through the loop portion for cooling and dehumidifying the first volume of air.
 2. The apparatus of claim 1, wherein the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof.
 3. The apparatus of claim 2, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value.
 4. The apparatus of claim 2, wherein the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value.
 5. The apparatus of claim 2, wherein the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value.
 6. The apparatus of claim 1 further comprising a water source having an associated pressure valve, and a nozzle configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane.
 7. The apparatus of claim 6, wherein the controller is adapted to set a water pressure of the water source.
 8. The apparatus of claim 1 further comprising a water nozzle disposed within the dry passage and adapted to dispense condensed water from the first volume of air.
 9. The apparatus of claim 8, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water.
 10. A method of dynamically cycling air in an indirect evaporative cooler, the method comprising: having a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; selectively passing intake air from the intake portion, recirculation air from the loop portion, or a combination thereof by a mixing valve disposed in the dry passage; moving air into and through the loop portion by a first fan disposed downstream of the mixing valve; selectively passing outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof by a diverting valve disposed in the dry passage; and circulating air a number of loop circuits through the loop portion for cooling and dehumidifying the first volume of air by a controller adapted to operate the mixing valve, the first fan, the diverting valve, and a combination thereof.
 11. The method of claim 10, wherein the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof.
 12. The method of claim 11, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value.
 13. The method of claim 11, wherein the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value.
 14. The method of claim 11, wherein the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value.
 15. The method of claim 10 further comprising wetting the wet passage by a water source having an associated pressure valve and a nozzle, for evaporative cooling of the substantially liquid-impermeable membrane.
 16. The method of claim 15, wherein the controller is adapted to set a water pressure of the water source.
 17. The method of claim 10 further comprising dispensing condensed water from the first volume of air by a water nozzle disposed within the dry passage.
 18. The method of claim 17, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water.
 19. A system for dynamically cycling air, the system comprising: an evaporative liquid reservoir comprising a pressure valve and a channel adapted to transport evaporative liquid; a heat exchanger comprising: a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a nozzle coupled with the channel and configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; and a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the pressure valve, the mixing valve, the diverting valve, and a combination thereof, to circulate air a number of loop circuits through the loop portion for cooling and dehumidifying a first volume of air.
 20. The system of claim 19 further comprising a first fan disposed downstream of the mixing valve and adapted to move the first volume of air into and through the loop portion.
 21. The system of claim 19 wherein the number of loop circuits is based on one of dry passage air temperature, dry passage air relative humidity, or a combination thereof.
 22. The system of claim 21, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion upon detection of dry passage air relative humidity being at or above a threshold value.
 23. The system of claim 21, wherein the controller is adapted to close the mixing valve from passing intake air and the diverting valve from passing outlet air upon detection of dry passage air temperature being at or above a threshold value.
 24. The system of claim 21, wherein the controller is adapted to open the mixing valve for passing intake air and the diverting valve for passing outlet air upon detection of dry passage air temperature being below a threshold value.
 25. The system of claim 19, wherein the controller is adapted to set a water pressure of the evaporative liquid reservoir.
 26. The system of claim 19 further comprising a water nozzle disposed within the dry passage and adapted to dispense condensed water from the first volume of air.
 27. The system of claim 26, wherein the controller is adapted to open the mixing valve and to close the diverting valve in order to pass intake air and to increase pressure in the loop portion for dispensing condensed water. 